Washington — Turkey with swiss, hold the mayo. Tuna and extra peppers. Grilled cheese with tomato. Everything that Kevin McCarthy needs to know to clinch his lead in the race for the No. 2 Republican job in the US House, he learned at the deli he started as a young man in Bakersfield, Calif.

Well, maybe not everything, but the key thing – personal relations.

It’s a lot easier to run a successful sandwich shop if you know your customers – their sandwich preferences, their kids’ names, their favorite sports. And you can’t win a leadership election on Capitol Hill without knowing the people in your party, and knowing them really well.

“This is all relationship driven,” says Rep. Devin Nunes (R) of California, speaking about the race to replace Rep. Eric Cantor as Republican majority leader, the next-in-line to House Speaker John Boehner of Ohio. Mr. Cantor lost his Virginia primary race June 10 in an upset to Dave Brat, who is further to his right.

What members consider in potential leaders is who they’re closest to, what incoming class they were in, what committees they’ve served on, who they’ve worked with – not necessarily policy issues, says Congressman Nunes, whose district, like Representative McCarthy’s, lies in California’s central valley.

The two are friends, and of course, Nunez is going to back McCarthy, who is now the party whip, the No. 3 job in the leadership. The whip’s responsibility is to secure votes.

Eager to move up, McCarthy quickly set his whipping operation in motion, and by the end of the day Thursday – just one day after Cantor announced his resignation from leadership – the affable Californian appeared to have his votes, with his only announced competitor at that time, Pete Sessions of Texas, dropping out late in the day. The actual election isn’t until June 19.

On Friday, a more conservative Republican, Rep. Raúl Labrador of Idaho, announced that he, too, is running for majority leader. Congressman Labrador rode into Congress on the tea party wave of 2010. The defeat of Cantor, he said in a statement announcing his candidacy, showed that, "Americans don’t believe their leaders in Washington are listening, and now is the time to change that."

At this point, it’s difficult to imagine Labrador besting McCarthy, but his vote will gauge the strength of the far-right faction in the House. A closer race now appears to be for McCarthy’s slot, a three-way competition that includes Rep. Steve Scalise of Louisiana, the chair of the conservative Republican Study Group.

The whip job has given McCarthy a tremendous advantage in this race. No other task in GOP leadership puts someone as close to all 233 members as gathering votes. But it’s McCarthy’s affability, personal relations with members, and political skill that are likely to account for his quick ascent to Cantor’s job next week, according to those who know him.

“He’s an impossible guy not to like personally,” says Rep. Tom Cole (R) of Oklahoma, another McCarthy supporter. “He’s a unifier, not a divider.”

According to media reports, the father of two children works out with members in the House gym, rides bikes with them through Rock Creek Park and along the famed C&O Canal, invites them to small dinners, and knows their spouses and kids. He makes members welcome in his first-floor whip office at the Capitol, where he sleeps on his sofa.

McCarthy works hard, visiting members’ districts, attempts to mend fences with those who don’t agree with him, and is often on the phones with donors, members, and friends. He’s experienced at network building, and was head of recruiting for the National Republican Congressional Committee during the 2010 election cycle. That’s the one that swept Republicans, including a wave of tea partiers, into control of the House – and him into the job as whip, even though he was only elected to Congress in 2006.

McCarthy’s whipping activities have not always been successful. He could not deliver for Speaker Boehner’s financial packages in 2011 and 2012 – when tea party conservatives were so riled up about the debt and the debt ceiling. Indeed, McCarthy himself broke with the speaker in the final “fiscal cliff” deal of 2012.

And policy is not considered his strength, though he has adopted two specialties – technology (think Silicon Valley) and energy. That comparative weakness could be a challenge for him as the majority leader, who sets the agenda for what comes to the floor.

One thing for sure. He thinks regulations are suffocating small business. It's something he learned as the owner of a small deli. And he hasn't forgotten it.